Mixed-dimensional vertical Bi2O2Se nanopillars/Si heterojunctions with the light confinement effect for high-performance photodetection

Abstract

Bi₂O₂Se is considered to be a promising layered semiconductor material in the post-graphene era due to its high mobility, moderate bandgap, excellent air stability, and compatibility with current electronic industries. Heterojunctions based on Bi₂O₂Se, formed by introducing energy band-aligned heterogeneous semiconductor materials, exhibit significant potential for self-powered photodetection applications. However, currently all the reported Bi₂O₂Se-based heterojunctions are integrated in thin-layer configurations along Bi₂O₂Se's basal plane. Their photoelectric conversion performance is still limited by weak light absorption in thin-layer Bi₂O₂Se heterojunctions. To address this, we demonstrate a novel mixed-dimensional vertical Bi₂O₂Se nanopillars/Si heterojunction-based photodetector, achieved by depositing one-dimensional n-type Bi₂O₂Se nanopillars on three-dimensional p-type Si wafers via magnetron sputtering. The light confinement effect of the vertical Bi₂O₂Se nanopillars extends the light transmission path within Bi₂O₂Se, effectively mitigating the high reflectivity of planar silicon and the high transmittance of thin-layer Bi₂O₂Se, thereby enhancing the heterojunction's light absorption. The built-in electric field directed from n-type Bi₂O₂Se to p-type Si, combined with well-matched energy bands, facilitates the efficient separation of photogenerated electron–hole pairs, improving the photoelectric conversion efficiency and response speed of the heterojunction. The heterojunction photodetector exhibits self-powered characteristics, with a specific detectivity reaching 4.2 × 10¹² Jones and rapid rise/fall times of 24/40 μs. Furthermore, the heterojunction photodetector demonstrates a broad spectral response, spanning from the ultraviolet to visible to near-infrared light region. Our work paves the way for the development of high-performance optoelectronic devices based on new-generation mixed-dimensional layered semiconductor materials.